Polarizing plate and liquid crystal display comprising the same

ABSTRACT

A polarizing plate and a liquid crystal display including the same are provided. A polarizing plate includes: a polarizer; and a pattern layer on a light exit surface of the polarizer, the pattern layer including a first resin layer and a second resin layer sequentially arranged on the polarizer, a pattern portion being located at an interface between the first resin layer and the second resin layer and being composed of at least two pattern groups repeatedly arranged therein, each of the pattern groups including at least two engraved optical patterns; and at least two of the engraved optical patterns in each of the pattern groups having different aspect ratios and different base angles.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2018-0104006, filed on Aug. 31, 2018, and KoreanPatent Application No. 10-2019-0096380, filed on Aug. 7, 2019, in theKorean Intellectual Property Office, the entire disclosure of both ofwhich are incorporated herein by reference.

FIELD

Aspects of embodiments of the present invention relate to a polarizingplate and a liquid crystal display including the same.

DESCRIPTION OF THE RELATED ART

A liquid crystal display is operated to allow light emitted from abacklight unit to sequentially pass through a light source-sidepolarizing plate, a liquid crystal panel, and a viewer-side polarizingplate. Light emitted from a light source spreads while passing throughthe backlight unit and then enters the light source-side polarizingplate. As a result, the liquid crystal display suffers from gradualdeterioration in contrast ratio and color deviation from a front side toa lateral side while light passes through the light source-sidepolarizing plate, the liquid crystal panel, and the viewer-sidepolarizing plate. To address such problems, a retardation film may beapplied to the light source-side polarizing plate or the viewer-sidepolarizing plate. However, it is difficult for the retardation film toachieve complete compensation of light from the front side to thelateral side and to prevent light leakage, particularly in a diagonaldirection.

In order to address the aforementioned problems, use of alight-collecting backlight unit is suggested. The light-collectingbacklight unit employs an inverted prism light-collecting sheet insteadof a typical normal prism diffusion sheet. The normal prism diffusionsheet is a sheet having a prism formed on a light exit surface of asheet member, and the inverted prism light-collecting sheet is a sheethaving a prism on a light incident surface of a sheet member. Thistechnique is a light collecting-scattering system that minimizes orreduces difference in contrast ratio depending upon viewing angle byallowing light emitted from the light-collecting backlight unit throughlight collection to pass through a liquid crystal panel and securesviewing angle by scattering light at the outermost surface of theviewer-side polarizing plate. To this end, there is a need fordevelopment of an optical device in consideration of thelight-collecting backlight unit. Although a scatteringparticle-containing film may be used as the optical device to bedisposed on the outermost surface of the viewer-side polarizing plate,there is a limitation in terms of enlargement of viewing angle of thescattering particle-containing film and/or improvement in externalappearance thereof.

The background technique of the present invention is disclosed inJapanese Unexamined Patent Publication No. 2006-251659.

SUMMARY

According to an aspect of embodiments of the present invention, apolarizing plate is capable of improving brightness, viewing angle, andcontrast ratio at a front side and a lateral side in application to aliquid crystal display including a light-collecting backlight unit.

According to another aspect of embodiments of the present invention, apolarizing plate is capable of improving front contrast ratio, lateralcontrast ratio, and external appearance in application to a liquidcrystal display including a light-collecting backlight unit.

According to another aspect of embodiments of the present invention, apolarizing plate is capable of reducing deviation in ratio of brightnessat a lateral side to brightness at a front side depending upon an angleof the lateral side in application to a liquid crystal display includinga light-collecting backlight unit.

According to another aspect of embodiments of the present invention, aliquid crystal display includes a light-collecting backlight unit, hasimproved brightness, viewing angle, and contrast ratio at a front sideand a lateral side, and has reduced deviation in ratio of brightness ata lateral side to brightness at a front side depending upon an angle ofthe lateral side.

In accordance with one or more embodiments of the present invention, apolarizing plate includes: a polarizer; and a pattern layer on a lightexit surface of the polarizer, wherein the pattern layer includes afirst resin layer and a second resin layer sequentially arranged on thepolarizer, and a pattern portion is located at an interface between thefirst resin layer and the second resin layer and is composed of at leasttwo pattern groups repeatedly arranged therein, each of the patterngroups including at least two engraved optical patterns, and at leasttwo of the engraved optical patterns in each of the pattern groups havedifferent aspect ratios and different base angles.

The engraved optical patterns may have an aspect ratio of about 0.3 toabout 3.0.

The engraved optical patterns in the pattern groups may have adifference of about 0.5 or more between a maximum aspect ratio and aminimum aspect ratio.

The engraved optical patterns may have a base angle of about 60° toabout 90°.

The engraved optical patterns in the pattern groups may have adifference of about 5° or more between a maximum base angle and aminimum base angle.

The engraved optical patterns may have a flat surface at a top portionthereof and an N-sided polygonal cross-sectional shape, N being aninteger from 4 to 10.

The engraved optical patterns in the pattern groups may be consecutivelyarranged without a flat section therebetween.

A flat section may be absent or may be further formed between twoimmediately adjacent pattern groups.

The engraved optical patterns may extend in a stripe shape in alongitudinal direction thereof.

An angle defined between a longitudinal direction of the engravedoptical pattern and an absorption axis of the polarizer may be about−20° to about 20°, from about 70° to about 110°, or from about −70° toabout −110°, wherein the absorption axis of the polarizer is defined as0°.

The first resin layer may have a higher refractive index than the secondresin layer.

An absolute value of a difference in refractive index between the firstresin layer and the second resin layer may be about 0.05 or more.

A number of the engraved optical patterns in each pattern group may befrom 2 to 10.

Each of the pattern groups may be composed of a total of two opticalpatterns comprising a first pattern and a second pattern as the engravedoptical patterns, and the first pattern and the second pattern may havedifferent base angles and different aspect ratios.

Each of the pattern groups may be composed of a total of three opticalpatterns comprising a first pattern, a second pattern, and a thirdpattern consecutively arranged without a flat section therebetween, asthe engraved optical patterns, and at least two of the first pattern,the second pattern, and the third pattern may have different base anglesand different aspect ratios.

The first resin layer may be a filling portion filling at least part ofthe engraved optical patterns, or a layer including the filling portion.

The polarizing plate may further include a protective film stacked on atleast one of a light exit surface and a light incident surface of thepattern layer.

The polarizing plate may further include at least one surface treatmentlayer selected from among a hard coating layer, a scattering layer, alow reflectivity layer, an ultra-low reflectivity layer, a primer layer,an anti-fingerprint layer, an antireflection layer, and an antiglarelayer on at least one surface of the protective film.

In accordance with one or more embodiments of the present invention, aliquid crystal display includes a polarizing plate according to thepresent invention.

The liquid crystal display may include a backlight unit, a lightsource-side polarizing plate, a liquid crystal panel, and the polarizingplate sequentially stacked in the stated order, and the backlight unitmay include a light-collecting backlight unit including an invertedprism sheet.

In a white mode of the light-collecting backlight unit, a ratio(W_(30°)=L_(30°)/L_(0°)) of brightness (L_(30°)) at a lateral side (30°or −30°) to brightness (L_(0°)) at a front side (0°) may be from about0.1 to about 0.5, and a ratio (W_(60°)=L_(60°)/L_(0°)) of brightness(L_(60°)) at a lateral side (60° or −60°) to brightness (L_(0°)) at thefront side (0°) may be from about 0 to about 0.1.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a polarizing plate according to anembodiment of the present invention.

FIG. 2 is a cross-sectional view of a pattern group of the polarizingplate of FIG. 1.

FIG. 3 is a cross-sectional view of a pattern group of a polarizingplate according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a pattern group of a polarizingplate according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a polarizing plate according toanother embodiment of the present invention.

FIG. 6 is a cross-sectional view of a polarizing plate according toanother embodiment of the present invention.

FIG. 7 is a cross-sectional view of a pattern group of a polarizingplate according to yet another embodiment of the present invention.

FIG. 8 shows brightness profiles depicting a ratio of brightness at alateral side to brightness (L_(0°)) at a front side (0°) with respect tolight emitted from a light-collecting backlight unit and a typicalbacklight unit in a white mode.

FIG. 9 is a cross-sectional view of a light-collecting backlight unitaccording to an embodiment of the present invention.

FIG. 10 is a cross-sectional view of a polarizing plate of ComparativeExample 4.

FIG. 11 to FIG. 18 show a brightness profile (solid line) of alight-collecting backlight unit and brightness profiles (dash-dottedline) in application of polarizing plates of Examples to thelight-collecting backlight unit.

FIG. 19 to FIG. 22 show a brightness profile (solid line) of alight-collecting backlight unit and brightness profiles (dash-dottedline) in application of polarizing plates of Comparative Examples to thelight-collecting backlight unit.

FIG. 23 shows a ratio (solid line) of brightness at a lateral side tobrightness at a front side with respect to light emitted from a typicalbacklight unit and a brightness profile (dash-dotted line) inapplication of a polarizing plate of Example 4 to a typical backlightunit.

DETAILED DESCRIPTION

Some example embodiments of the present invention will be described infurther detail with reference to the accompanying drawings to provide athorough understanding of the invention to those skilled in the art. Itis to be understood that the present invention may be embodied indifferent ways and is not limited to the following embodiments. In thedrawings, portions irrelevant to the description may be omitted forclarity. Like components will be denoted by like reference numeralsthroughout the specification.

Herein, spatially relative terms, such as “upper” and “lower,” aredefined with reference to the accompanying drawings. Thus, it is to beunderstood that the term “upper surface” can be used interchangeablywith the term “lower surface,” for example, and when an element, such asa layer or a film, is referred to as being placed “on” another element,it may be directly placed on the other element, or one or moreintervening elements may be present. On the other hand, when an elementis referred to as being placed “directly on” another element, there areno intervening element(s) therebetween.

Herein, the terms “horizontal direction” and “vertical direction” mean alongitudinal direction and a transverse direction of a rectangularscreen of a liquid crystal display, respectively. Herein, “lateral side”refers to −30°, −45°, −60°, 30°, 45°, or 60° in a system in which afront side is indicated by 0°, a left end point is indicated by −90°,and a right end point is indicated by 90° with reference to thehorizontal direction.

Herein, “top portion” refers to the highest point of an engraved opticalpattern.

Herein, “aspect ratio” refers to a ratio of the maximum height of anengraved optical pattern to the maximum width thereof (maximumheight/maximum width).

Herein, “base angle” means an angle defined between the maximum width ofan optical pattern and a slanted surface directly connected to themaximum width thereof. For example, referring to FIG. 2, the base anglemeans an angle α1 defined between the maximum width W1 of an opticalpattern 230A and a slanted surface 231 directly connected to the maximumwidth W1 of the optical pattern 230A. For example, referring to FIG. 3,the base angle means an angle α1 defined between the maximum width W1 ofan optical pattern 240A and a slanted surface 241 directly connected tothe maximum width W1 of the optical pattern 240A.

Herein, “in-plane retardation (Re)” is a value measured at a wavelengthof 550 nm and is represented by Equation A:Re=(nx−ny)×d,where nx and ny are the indices of refraction in the slow and fast axesof a protective layer at a wavelength of 550 nm, respectively, and d isthe thickness (unit: nm) of the protective layer.

Herein, the term “(meth)acryl” refers to acryl and/or methacryl.

Unless specifically stated otherwise, a lateral side (30°) may mean atleast one of a lateral side of 30° and a lateral side of −30°, a lateralside (45°) may mean at least one of a lateral side of 45° and a lateralside of −45°, and a lateral side (60°) may mean at least one of alateral side of 60° and a lateral side of −60°.

FIG. 8 shows a brightness profile (dash-dotted line in FIG. 8) depictinga ratio of brightness at a lateral side to brightness (L_(0°)) at afront side (0°) with respect to light emitted from a light-collectingbacklight unit in a white mode and a brightness profile (solid line inFIG. 8) depicting a ratio of brightness at a lateral side to brightness(L_(0°)) at a front side (0°) with respect to light emitted from atypical backlight unit in a white mode.

According to embodiments of the present invention, for thelight-collecting backlight unit, in a white mode, a ratio(W_(30°)=L_(30°)/L_(0°)) of brightness (L_(30°)) at a lateral side (30°or −30°) to brightness (L_(0°)) at a front side (0°) may be about 0.1 toabout 0.5, and, in an embodiment, 0.1 to 0.15, and, in an embodiment,0.11, and a ratio (W_(60°)=L_(60°)/L_(0°)) of brightness (L_(60°)) at alateral side (60° or −60°) to brightness (L_(0°)) at a front side (0°)may be about 0 to about 0.1, and, in an embodiment, about 0 to about0.05, and, in an embodiment, about 0.

For the typical backlight unit, in a white mode, a ratio(W_(30°)=L_(30°)/L_(0°)) of brightness (L_(30°)) at a lateral side (30°or −30°) to brightness (L_(0°)) at a front side (0°) may be 0.5 to 0.6,for example, greater than 0.5 to about 0.6 or less, and a ratio(W_(60°)=L_(60°)/L_(0°)) of brightness (L_(60°)) at a lateral side (60°or −60°) to brightness (L_(0°)) at a front side (0°) may be about 0.1 toabout 0.2.

As such, the light-collecting backlight unit according to embodiments ofthe present invention exhibits a completely different brightness profilethan the typical backlight unit, as shown in FIG. 8. The “typicalbacklight unit” means a backlight unit not including an inverted prismlight-collecting sheet, specifically, a backlight unit including anormal prism diffusion sheet.

According to embodiments of the present invention, as a viewer-sidepolarizing plate configured to emit light received from alight-collecting backlight unit including an inverted prism, theviewer-side polarizing plate includes a polarizer and a pattern layerformed on a light exit surface of the polarizer, wherein the patternlayer includes a first resin layer, a second resin layer, and a patternportion having pattern groups repeatedly arranged at an interfacebetween the first resin layer and the second resin layer, therebyimproving brightness, viewing angle, and contrast ratio at a front sideand a lateral side while reducing deviation in ratio of brightness atthe lateral side to brightness at the front side depending upon an angleof the lateral side in application to a liquid crystal display includinga light-collecting backlight unit.

The pattern group is composed of at least two engraved optical patterns,in which at least two of the engraved optical patterns have differentaspect ratios and different base angles.

Herein, a polarizing plate according to an embodiment of the presentinvention will be described with reference to FIG. 1 and FIG. 2. FIG. 1is a cross-sectional view of a polarizing plate according to anembodiment of the present invention; and FIG. 2 is a cross-sectionalview of a pattern group of the polarizing plate of FIG. 1.

Referring to FIG. 1, a polarizing plate 10 includes a polarizer 100, apattern layer 200 formed on a light exit surface (upper surface) of thepolarizer 100, and a protective film 300 formed on an upper surface ofthe pattern layer 200.

As manufactured by excluding the protective film 300 for the purpose ofsimplification of a manufacturing process and thickness reduction, apolarizing plate including the pattern layer 200 formed only on theupper surface of the polarizer 100 without the protective film 300 isalso within the scope of the present invention.

In other embodiments, the protective film 300 may be interposed betweenthe polarizer 100 and the pattern layer 200. That is, according toembodiments of the present invention, the location of the protectivefilm in the polarizing plate is not particularly limited.

Pattern Layer

In an embodiment, the pattern layer 200 is formed between the polarizer100 and the protective film 300 to allow polarized light received fromthe polarizer 100 to enter the protective film 300 therethrough.

The pattern layer 200 may include a first resin layer 210 and a secondresin layer 220 disposed to face the first resin layer 210. In anembodiment, the pattern layer 200 may consist of the first resin layer210 and the second resin layer 220, which directly contact each other.

The first resin layer 210 is formed on a light incident surface of thesecond resin layer 220. A pattern portion described herein may be formedat an interface between the first resin layer 210 and the second resinlayer 220.

The pattern portion is composed of at least two pattern groups 230repeatedly arranged. In the pattern portion, the pattern groups 230 maybe the same as each other or may be different from each other.

Although FIG. 1 shows a polarizing plate in which no flat section isformed between the pattern groups 230, a flat section may be formedbetween the pattern groups 230. The structure will be described infurther detail below.

In an embodiment, the pattern group 230 is composed of at least twoengraved optical patterns consecutively arranged without a flat sectiontherebetween, in which at least two of the engraved optical patternshave different aspect ratios and different base angles. With a structurewherein at least two of the engraved optical patterns have the sameaspect ratio despite having different base angles, the polarizing platemay exhibit less improvement in viewing angle at all of lateral sides30°, 45°, and 60°, or abnormally high or low brightness at a certainangle to provide uneven image quality at a lateral side. With astructure wherein at least two of the engraved optical patterns have thesame base angle despite having different aspect ratios, the polarizingplate can suffer from the same problems.

In an embodiment, referring to FIG. 2, the pattern group 230 includesthree optical patterns, that is, a first pattern 230A, a second pattern230B, and a third pattern 230C, consecutively arranged without a flatsection therebetween. At least two of the first pattern 230A, the secondpattern 230B, and the third pattern 230C have different aspect ratiosand different base angles.

Herein, as shown in FIG. 2, although any base angle may be defined asthe base angle in a case in which both base angles of each of the firstpattern 230A, the second pattern 230B, and the third pattern 230C arethe same, a larger base angle among both base angles may be defined asthe base angle in a case in which both base angles of each of the firstpattern 230A, the second pattern 230B, and the third pattern 230C aredifferent.

FIG. 1 and FIG. 2 show the polarizing plate wherein the engraved opticalpatterns are consecutively arranged in each pattern group without a flatsection therebetween. In other embodiments, however, the pattern groupmay include a flat section between the engraved optical patterns, asdescribed in further detail below.

In an embodiment, the first pattern, the second pattern, and the thirdpattern may have different base angles and different aspect ratios.

In another embodiment, the first pattern and the second pattern may havedifferent base angles and different aspect ratios.

In another embodiment, the first pattern and the third pattern may havedifferent base angles and different aspect ratios.

In another embodiment, the second pattern and the third pattern may havedifferent base angles and different aspect ratios.

In an embodiment, the optical patterns are consecutively arranged in asequence of increasing base angles in the pattern group. That is,referring to FIG. 2, a base angle (α1) of the first pattern 230A is lessthan a base angle (α2) of the second pattern 230B, which is less than abase angle (α3) of the third pattern 230C. In an embodiment, an aspectratio of the first pattern 230A may be less than an aspect ratio of thesecond pattern 230B; an aspect ratio of the third pattern 230C may beless than or equal to the aspect ratio of the second pattern 230B; andthe aspect ratio of the first pattern 230A may be less than or equal tothe aspect ratio of the third pattern 230C.

Although FIG. 2 shows the pattern group 230 including three engravedoptical patterns, the number of optical patterns in each of the patterngroups may be adjusted or selected depending upon the degree ofcollecting light emitted from a light-collecting backlight unit,brightness, thickness of the polarizing plate, and the like. Forexample, the number of engraved optical patterns in each pattern groupmay be about 2 to about 10, and, in an embodiment, from 2 to 5, and, inan embodiment, from 2 to 3.

In an embodiment, interfacial points between the first pattern 230A, thesecond pattern 230B, and the third pattern 230C provided as the engravedoptical patterns in in the pattern group may contact each other and maybe disposed coplanar to each other.

An aspect ratio of each of the first pattern 230A, the second pattern230B, and the third pattern 230C, or an average aspect ratio of thepatterns in the pattern group, may be about 0.3 to about 3.0, forexample about 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3,1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7,2.8, 2.9, or 3.0, and, in an embodiment, about 1.0 to about 3.0, and, inan embodiment, about 1.0 to about 2.0. Within this range, the polarizingplate can have improved viewing angle and can exhibit uniform lateralbrightness.

In an embodiment, a difference between a maximum aspect ratio and aminimum aspect ratio of the engraved optical patterns, that is, thefirst pattern, the second pattern, and the third pattern, in the patterngroup may be about 0.5 or more, for example, about 0.5, 0.6, 0.7, 0.8,0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2,2.3, 2.4, 2.5, and, in an embodiment, about 0.5 to about 2.5, and, in anembodiment, about 0.5 to about 1.0. Within this range, the polarizingplate can achieve improvement in viewing angle and uniform lateralbrightness.

In an embodiment, a base angle α1, α2, or α3 of each of the firstpattern 230A, the second pattern 230B, and the third pattern 230C, or anaverage value of base angles of the patterns in the pattern group may beabout 60° to about 90°, for example about 60°, about 65°, about 70°,about 75°, about 80°, about 85°, or about 90°, and, in an embodiment,about 60° to less than about 90°, and, in an embodiment, about 75° toabout 85°. Within this range, the polarizing plate can achieveimprovement in viewing angle and uniform lateral brightness.

In an embodiment, a difference between a maximum base angle and aminimum base angle of the optical patterns, that is, the first pattern,the second pattern, and the third pattern, in the pattern group may beabout 5° or more, for example, about 5°, 6, 7°, 8, 9°, 10°, 11°, 12°,13°, 14°, 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, or 25°, and,in an embodiment, about 5° to about 25°, and, in an embodiment, about 5°to about 10°. Within this range, the polarizing plate can achieveimprovement in viewing angle and uniform lateral brightness.

Both base angles of each of the first pattern, the second pattern, andthe third pattern may be the same or different. In an embodiment, bothbase angles of each of the first pattern, the second pattern, and thethird pattern are the same.

Maximum widths W1, W2, W3 of the first pattern 230A, the second pattern230B, and the third pattern 230C, respectively, may be the same ordifferent. For example, each of the maximum widths W1, W2, W3 may beabout 1 μm to about 50 μm, for example, about 1 μm to about 20 μm.Within this range, the polarizing plate can achieve improvement inviewing angle and uniform lateral brightness, and can prevent orsubstantially prevent a pixel Moiré phenomenon with a liquid crystalpanel.

Maximum heights h1, h2, h3 of the first pattern 230A, the second pattern230B, and the third pattern 230C, respectively, may be the same ordifferent. For example, each of the maximum heights h1, h2, h3 may beabout 1 μm to about 50 μm, for example, about 1 μm to about 20 μm.Within this range, the polarizing plate can achieve improvement inviewing angle and uniform lateral brightness, and can prevent orsubstantially prevent a pixel Moiré phenomenon with a liquid crystalpanel.

FIG. 2 shows the first pattern 230A, the second pattern 230B, and thethird pattern 230C each having a trapezoidal cross-sectional shape inwhich slanted surfaces 231, 232, or 233 are connected to a flat surfaceat a top portion of each pattern. However, it is to be understood thatthe present invention is not limited thereto. Although the flat surfacecan be modified to have a surface roughness or a curved surface, in anembodiment, the flat surface does not have such a modification.

The engraved optical pattern may have a flat slanted surface or anangulated slanted surface, and may be a pattern having an N-sidedpolygonal (N being an integer from 4 to 10) cross-sectional shapeincluding a triangular cross-sectional shape or a trapezoidalcross-sectional shape with a flat surface at a top portion thereof. Thiswill be described in further detail below. In an embodiment, the opticalpatterns may have a trapezoidal cross-section.

In each of the pattern groups, the optical patterns may have the sameshape or different shapes. In an embodiment, the optical patterns havethe same shape, such that a process of manufacturing the polarizingplate is facilitated.

In FIG. 2, the flat surfaces of the first pattern 230A, the secondpattern 230B, and the third pattern 230C may have the same width ordifferent widths, and may have a width of greater than 0 μm and about 50μm or less, for example, about 1 μm to about 20 μm, and, in anembodiment, about 1 μm to about 10 μm. Within this range, the polarizingplate can achieve improvement in viewing angle and uniform lateralbrightness, and can prevent or substantially prevent a pixel Moiréphenomenon with a liquid crystal panel.

Referring again to FIG. 1, the pattern portion is composed of thepattern groups 230 repeatedly arranged therein. FIG. 1 shows thepolarizing plate in which the first pattern, the second pattern, and thethird pattern are arranged in the same sequence in each of the patterngroups. However, it is to be understood that the arrangement sequence ofthese optical patterns may be the same or different in adjacent patterngroups.

Although not shown in FIG. 1, each of the optical patterns in thepattern group may have a stripe shape extending in a longitudinaldirection of the optical pattern. With this structure, the polarizingplate can achieve improvement in viewing angle at lateral sides. Herein,the “longitudinal direction of the optical pattern” means a differentdirection from the direction of the maximum width of the opticalpattern, that is, a direction intersecting therewith.

In an embodiment, assuming that the polarizer has an absorption axis of0°, an angle defined between the longitudinal direction of the opticalpattern and the absorption angle of the polarizer 100 may be in a rangefrom about −20° to about 20°, from about 70° to about 110°, or fromabout −70° to about −110°. Within this range, the polarizing plate canprevent or substantially prevent a pixel Moiré phenomenon with a liquidcrystal panel. In an embodiment, the angle defined therebetween is in arange from about 90° or about −90°.

In an embodiment, the first resin layer 210 may be a high-refractivitypattern layer having a higher refractive index than the second resinlayer 220.

In an embodiment, an absolute value of a difference in refractive indexbetween the first resin layer 210 and the second resin layer 220 may beabout 0.05 or more, and, in an embodiment, about 0.1 or more, and, in anembodiment, about 0.1 to about 0.3, about 0.1 to about 0.2, or about0.15 to about 0.2. Within this range, the polarizing plate can achieveimprovement in viewing angle.

In an embodiment, the first resin layer 210 may have a refractive indexof about 1.50 to about 1.70, and, in an embodiment, about 1.55 to about1.70, and, in an embodiment, about 1.60 to about 1.70. Within thisrange, the polarizing plate can have a high light spreading effect, canbe easily manufactured, and can achieve improvement in spreading ofpolarized light and viewing angle.

The first resin layer 210 may include a filling portion filling at leastpart of the engraved optical patterns or a layer having the fillingportion. In an embodiment, the filling portion completely fills theengraved optical patterns. In a structure in which the filling portionpartially fills the engraved optical patterns, the remaining portion ofthe engraved optical patterns may be filled with air.

The first resin layer 210 may be formed of a composition for the firstresin layer, which includes a curable resin. The curable resin mayinclude at least one selected from among a UV-curable resin and aheat-curable resin, without being limited thereto. The composition forthe first resin layer may further include at least one selected fromamong an initiator and an additive. The initiator may include at leastone selected from among a photocurable initiator and a heat-curableinitiator, without being limited thereto. The additive may include anytypical additive known to those skilled in the art. For example, theadditive may include at least one selected from among a leveling agent,a surface regulator, an antioxidant, an antifoaming agent, a UVabsorbent, and a photo-stabilizer, without being limited thereto. Thecomposition for the first resin layer may further include a typicalsolvent for coatability, for example, ethanol, propylene glycolmonomethyletheracetate, methylethylketone, and methylisobutylketone,without being limited thereto.

In an embodiment, the first resin layer 210 may be a non-adhesive layer.When the first resin layer 210 is non-adhesive, the pattern layer may bestacked on an adherend, that is, on the polarizer, via an adhesiveagent, a bonding agent, or an adhesive/bonding agent.

In another embodiment, the first resin layer 210 may be an adhesivelayer. When the first resin layer 210 is an adhesive layer, the patternlayer may be stacked on the adherend without an additional adhesiveagent, a bonding agent, or an adhesive/bonding agent, thereby enablingreduction in thickness of the polarizing plate.

An upper surface of the second resin layer 220 may be a plane adjoiningthe protective film 300 and a lower surface thereof may be formed withthe engraved optical patterns corresponding to the pattern groups.

In an embodiment, the second resin layer 220 may be a low-refractivitypattern layer having a refractive index of about 1.3 to less than about1.50, and, in an embodiment, about 1.3 to about 1.49. Within this range,the polarizing plate can achieve improvement in viewing angle.

The second resin layer 220 may be formed of a composition for the secondresin layer, which includes a curable resin. The curable resin mayinclude at least one selected from among a UV-curable resin and aheat-curable resin, without being limited thereto. The composition forthe second resin layer may include at least one selected from among theinitiator, the additive, and the solvent described above.

In an embodiment, the second resin layer 220 may have a maximumthickness of greater than 0 μm to about 50 μm or less, for example,greater than 0 μm to about 30 μm or less. Within this range, thepolarizing plate can prevent or substantially prevent warpage, such ascurling.

In an embodiment, a value obtained by subtracting the maximum height ofthe optical pattern from the maximum thickness of the second resin layer220 (the maximum thickness of the second resin layer—the maximum heightof the optical pattern) (also referred to as “net thickness”) may begreater than 0 μm to about 30 μm or less, for example, greater than 0 μmto about 20 μm or less, or greater than 0 μm to about 10 μm or less.Within this range, the second resin layer can provide an effect ofincreasing surface hardness and can exhibit sufficient adhesion to theprotective film.

Protective Film

The protective film 300 is formed on a light exit surface of the patternlayer 200 to allow light having passed through the pattern layer 200 tobe emitted therethrough. The protective film 300 may support the patternlayer 200.

In an embodiment, the protective film 300 may be directly formed on thesecond resin layer 220 of the pattern layer 200, thereby enablingreduction in thickness of the polarizing plate 10. Herein, theexpression “directly formed on” means that any adhesive layer, bondinglayer, or adhesive/bonding layer is not interposed between theprotective film 300 and the pattern layer 200.

In an embodiment, the protective film 300 may have a total lighttransmittance of 90% or more, for example, 90% to 100%, in thewavelength band of visible light. Within this range, the protectivelayer allows transmission of light therethrough without affecting lightincident thereon.

The protective film 300 may include an optically transparent resin film,which includes a light incident surface and a light exit surface facingthe light incident surface. The protective film may be composed of asingle layer of a resin film or may be composed of multiple layers of aresin film. The resin may include at least one selected from amongcellulose ester resins including triacetyl cellulose (TAC), cyclicpolyolefin resins including amorphous cyclic olefin polymer (COP),polycarbonate resins, polyester resins including polyethyleneterephthalate (PET), polyethersulfone resins, polysulfone resins,polyamide resins, polyimide resins, non-cyclic polyolefin resins,poly(meth)acrylic resins including poly(methyl methacrylate), polyvinylalcohol resins, polyvinyl chloride resins, and polyvinylidene chlorideresins, without being limited thereto.

The protective film may be a non-stretched film, a retardation filmwhich is obtained by stretching the resin by a certain method to have acertain range of retardation, or an isotropic optical film. In anembodiment, the protective film may be an isotropic optical film havingan Re of about 0 nm to about 60 nm, and, in an embodiment, about 40 nmto about 60 nm. Within this range of Re, the protective film can providegood image quality through compensation for viewing angle. Herein, theterm “isotropic optical film” means a film having substantially the samenx, ny, and nz, (nz means a refractive index of the film in thethickness direction of the film) and the expression “substantially thesame” includes not only a case in which nx, ny and nz are completely thesame, but also a case in which there is an acceptable tolerance. Inanother embodiment, the protective film may be a retardation film havingan Re of about 60 nm or less. For example, the protective film may havean Re of about 60 nm to about 500 nm, or about 60 nm to about 300 nm. Inanother embodiment, the protective film may have an Re of about 6,000 nmor more, about 8,000 nm or more, and, in an embodiment, about 10,000 nmor more, and, in an embodiment, greater than about 10,000 nm, and, in anembodiment, about 10,100 nm to about 30,000 nm, and, in an embodiment,about 10,100 nm to about 15,000 nm. Within this range, the protectivefilm can prevent or substantially prevent generation of rainbow spotswhile further diffusing light diffused by a contrast improving layer.

In an embodiment, the protective layer 300 may have a thickness of about5 μm to about 200 μm, for example, about 30 μm to about 120 μm. Withinthis thickness range, the protective layer 300 can be used in thepolarizing plate.

Although not shown in FIG. 1, a surface treatment layer, such as any ofa hard coating layer, a scattering layer, a low reflectivity layer, anultra-low reflectivity layer, a primer layer, an anti-fingerprint layer,an antireflection layer, and an antiglare layer, may be further formedon at least one surface of the protective film 300 (at least one of anupper surface and a lower surface thereof). The surface treatment layercan provide further functions to the polarizing plate.

In an embodiment, with the pattern layer on the upper surface of thepolarizer, the polarizing plate 10 may have a total light transmittanceof about 40% or more, and, in an embodiment, about 40% to about 50%, anda degree of polarization of about 95% or more, and, in an embodiment,about 95% to about 100%. Within this range, the polarizing plate can besuitably used in a liquid crystal display.

Polarizer

The polarizer 100 may polarize light received from a liquid crystalpanel and allow the polarized light to travel to the pattern layer 200after passing therethrough. The polarizer 100 is formed on a lightincident surface of the pattern layer 200.

In an embodiment, the polarizer 100 may include a polyvinyl alcoholpolarizer obtained by uniaxially stretching a polyvinyl alcohol film, ora polyene-based polarizer obtained by dehydrating a polyvinyl alcoholfilm. In an embodiment, the polarizer 100 may have a thickness of about5 μm to about 40 μm. Within this range, the polarizer 100 can be usedfor an optical display.

The polarizing plate may include the polarizer 100 and a protective filmformed on at least one surface of the polarizer. The protective filmprotects the polarizer, thereby improving reliability and mechanicalstrength of the polarizing plate. The protective film may include a filmcomprising any of the resins mentioned above in description of theprotective film 300.

Although not shown in FIG. 1, an adhesive layer may be further formed ona lower surface of the polarizer 100 to attach the polarizing plate to aliquid crystal panel.

In an embodiment, the polarizing plate is configured to satisfy thefollowing Relations 1 and 2 in application to a light-collectingbacklight unit, thereby securing brightness uniformity while improvingviewing angle at a lateral side.W _(30°) >W _(45°) >W _(60°)  Relation 1W _(60°)>0.2  Relation 2where W_(30°) is a ratio of brightness (L_(30°)) at a lateral side (30°or −30°) to brightness (L_(0°)) at a front side (0°) in a white mode;W_(45°) is a ratio of brightness (L_(45°)) at a lateral side (45° or−45°) to brightness (L_(0°)) at the front side (0°) in a white mode; andW_(60°) is a ratio of brightness (L_(60°)) at a lateral side (60° or−60°) to brightness (L_(0°)) at the front side (0°) in a white mode.

Next, a polarizing plate according to another embodiment of the presentinvention will be described with reference to FIG. 3. FIG. 3 is across-sectional view of a pattern group of a polarizing plate accordingto another embodiment of the present invention.

Referring to FIG. 3, the polarizing plate according to this embodimentis substantially the same as the polarizing plate of FIG. 1 except thata pattern portion includes pattern groups 240 repeatedly arrangedtherein instead of the pattern groups 230.

The pattern group 240 is composed of a total of two engraved opticalpatterns comprising a first pattern 240A and a second pattern 240B,which are consecutively arranged without a flat section therebetween.The first pattern 240A and the second pattern 240B have different baseangles and different aspect ratios.

Referring to FIG. 3, each of the first pattern 240A and the secondpattern 240B has a trapezoidal shape in which slanted surfaces 241, 242are connected to each other by a flat surface at a top portion thereof.However, it is to be understood that the present invention is notlimited thereto. For example, the engraved optical patterns according tothis embodiment may have an N-sided polygonal cross-sectional shape, asdescribed above.

The shape, the base angle α1, the maximum width W1, the maximum heighth1, and the material of the first pattern 240A may be changed orselected as described with reference to FIG. 1 and FIG. 2, and theshape, the base angle α2, the maximum width W2, the maximum height h2,and the material of the second pattern 240B may be changed or selectedas described with reference to FIG. 1 and FIG. 2.

Next, a polarizing plate according to another embodiment of the presentinvention will be described with reference to FIG. 4. FIG. 4 is across-sectional view of a pattern group of a polarizing plate accordingto another embodiment of the present invention.

Referring to FIG. 4, the polarizing plate according to this embodimentis substantially the same as the polarizing plate of FIG. 1 except thata pattern portion includes pattern groups 250 repeatedly arrangedtherein instead of the pattern groups 230.

The pattern group 250 further includes flat sections 251, 252 betweenengraved optical patterns 230A, 230B, 230C. The flat sections 251, 252serve to improve transmittance by suppressing deterioration in frontbrightness.

In an embodiment, the flat sections 251, 252 may be arranged at a cyclicpitch (that is, a sum of the maximum width of one flat section and themaximum width of an engraved optical pattern immediately adjacent to theflat section) of about 1 μm to about 100 μm, and, in an embodiment,about 3 μm to about 50 μm, in the pattern group. Within this range, thepolarizing plate can prevent or substantially prevent a pixel Moiréphenomenon with a liquid crystal panel.

In the pattern group, a ratio of a total sum of the maximum widths ofthe flat sections to a total sum (W1+W2+W3) of the maximum widths of theengraved optical patterns may be about 0 to about 2, for example 0, 0.1,0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, 1.9, or 2.0, and, in an embodiment, greater than about 0 toabout 2, about 0 to about 1, or greater than about 0 to about 1. Withinthis range, the polarizing plate can achieve improvement in lateralviewing angle.

In an embodiment, the flat sections 251, 252 may have a maximum width ofabout 1 μm to about 20 μm, and, in an embodiment, about 1 μm to about 10μm. Within this range, the optical patterns can be easily formed whilesecuring suitable transmittance and improvement in viewing angle.

Although FIG. 4 shows the polarizing plate in which the flat sections251, 252 are formed between the engraved optical pattern 230A and theengraved optical pattern 230B and between the engraved optical pattern230B and the engraved optical pattern 230C, the flat section may beformed in at least one of these regions.

Next, a polarizing plate according to another embodiment of theinvention will be described with reference to FIG. 5. FIG. 5 is across-sectional view of a polarizing plate according to anotherembodiment of the present invention.

Referring to FIG. 5, the polarizing plate 20 according to thisembodiment is substantially the same as the polarizing plate 10described above except for a pattern layer 260 instead of the patternlayer 200.

In the pattern layer 260, each of flat sections 261, 262 are formedbetween adjacent pattern groups 230. The flat sections 261, 262 canfacilitate pattern formability and can secure suitable transmittance.

In the pattern group 230, a ratio of a width L of the flat sections 261,262 to the total sum (W1+W2+W3) of the maximum widths of the engravedoptical patterns or the total width of the pattern groups 230 may beabout 0 to about 1, for example 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, or 1, and, in an embodiment, greater than about 0 to about 1.Within this range, the flat sections 261, 262 can facilitate patternformability and can secure suitable transmittance.

In an embodiment, each of the flat sections 261, 262 may have a maximumwidth (L) of greater than 0 μm to about 200 μm or less, and, in anembodiment, greater than 0 μm to about 100 μm or less. Within thisrange, the flat sections 261, 262 can facilitate pattern formability andcan secure suitable transmittance.

Next, a polarizing plate according to another embodiment of theinvention will be described with reference to FIG. 6. FIG. 6 is across-sectional view of a polarizing plate according to embodiment ofthe present invention.

Referring to FIG. 6, the polarizing plate 30 according to thisembodiment is substantially the same as the polarizing plate 10described above except for a pattern layer 270 instead of the patternlayer 200.

The pattern layer 270 is substantially the same as the pattern layer ofthe polarizing plate 10 described above except that a first resin layer210 of the pattern layer 270 includes a filling portion completelyfilling the engraved optical patterns so as to extend farther than theengraved optical patterns in the thickness direction. Accordingly, amaximum thickness of the first resin layer may be greater than a maximumthickness of the engraved optical patterns in the pattern group.

Next, a polarizing plate according to another embodiment of theinvention will be described with reference to FIG. 7. FIG. 7 is across-sectional view of a pattern group of a polarizing plate accordingto another embodiment of the present invention.

Referring to FIG. 7, a pattern group 280 is composed of at least threeoptical patterns, that is, a first pattern 280A, a second pattern 280B,and a third pattern 280C, which are consecutively arranged without aflat section therebetween. At least two of the first pattern 280A, thesecond pattern 280B, and the third pattern 280C have different baseangles α1, α2, α3 and different aspect ratios h1/W1, h2/W2, h3/W3.

Each of the first pattern 280A, the second pattern 280B, and the thirdpattern 280C has a slanted surface 281, 282, 283 connected to both a topportion thereof and the maximum width thereof and composed of two planesangulated to each other. Although FIG. 7 shows an engraved patternhaving a hexagonal cross-section, it is to be understood that thepresent invention is not limited thereto.

Although not shown in FIG. 7, the polarizing plate shown in FIG. 7 mayalso further include such a flat section between the pattern groups orinside the pattern group.

Next, a polarizing plate according to another embodiment will bedescribed.

The polarizing plate according to this embodiment is substantially thesame as the polarizing plate according to the above embodiment exceptthat the first resin layer according to this embodiment is alow-refractivity pattern layer having a lower refractive index than thesecond resin layer. For description of the refractive index, refer tothe above description of the embodiment of FIG. 1.

A liquid crystal display according to the present invention includes apolarizing plate according to an embodiment of the present invention.

In an embodiment, the liquid crystal display according to the presentinvention may include the polarizing plate as a viewer-side polarizingplate disposed at a viewer side with respect to a liquid crystal panel.The “viewer-side polarizing plate” is a polarizing plate disposed at ascreen side, that is, at a side opposite to a light source, with respectto the liquid crystal panel.

In an embodiment, the liquid crystal display incudes a light-collectingbacklight unit, a light source-side polarizing plate, a liquid crystalpanel, and a viewer-side polarizing plate sequentially stacked in thestated order, in which the viewer-side polarizing plate may include thepolarizing plate according to an embodiment of the present invention.The “light source-side polarizing plate” is a polarizing plate disposedat a light source side.

The light-collecting backlight unit may be composed of a light source, alight guide plate, and a light-collecting sheet. In an embodiment,referring to FIG. 9, a light-collecting backlight unit 600 may becomposed of a light source 610, a light guide plate 620, and alight-collecting sheet 630.

The light source 610 and the light guide plate 620 may be a light sourceand a light guide plate, which are typically used in a liquid crystaldisplay. The light-collecting sheet 630 may include a base film and aninverted prism formed on a light incident surface of the base film. Theinverted prism can improve efficacy of light through total reflection oflight emitted from the light guide plate by the pattern shape. In anembodiment, the light-collecting sheet may be integrally attached to thelight source-side polarizing plate of the liquid crystal display.

Although not shown in FIG. 9, a reflective sheet may be further formedon a lower surface of the light guide plate 620 to achieve furtherimprovement in luminous efficacy.

The liquid crystal panel may employ a vertical alignment (VA) mode, anIPS mode, a patterned vertical alignment (PVA) mode, or asuper-patterned vertical alignment (S-PVA) mode, without being limitedthereto.

Next, the present invention will be described in further detail withreference to some examples. However, it should be noted that theseexamples are provided for illustration only and are not to be construedin any way as limiting the present invention.

Example 1

A first resin layer (high-refractivity layer) was formed of acomposition comprising a UV-curable resin (SHIN-A T&C Co., Ltd.) havinga refractive index of 1.62. A second resin layer (low-refractivitylayer) was formed of a composition comprising a UV-curable resin (SHIN-AT&C Co., Ltd.) having a refractive index of 1.47.

A coating layer was formed by depositing a composition for a secondresin layer to a predetermined thickness on one surface (light incidentsurface) of a polyethylene terephthalate (PET) film (TA044, thickness:80 μm, Toyobo Co., Ltd.) as a protective film. The second resin layerwas formed on the coating layer by applying an optical pattern theretousing a film having an optical pattern formed thereon, followed by UVcuring at 500 mJ/cm². Then, a first resin layer was formed on onesurface of the second resin layer by coating a composition for the firstresin layer, followed by UV curing at 500 mJ/cm². Next, a polarizerhaving a PET/PVA/COP triple layer structure was coupled to one surfaceof the first resin layer, thereby preparing a polarizing plate.

The following Table 1 shows one pattern group of a pattern portionformed at an interface between the first resin layer and the secondresin layer. In the pattern portion, the pattern groups are repeatedlyarranged without a flat section, as shown in FIG. 1.

Referring to Table 1, the pattern group was composed of a total of threepatterns, that is, a first pattern, a second pattern, and a thirdpattern, which are sequentially arranged in the stated order without aflat section therebetween. Each of the first pattern, the secondpattern, and the third pattern is an engraved optical pattern having atrapezoidal cross-section. Each of the first pattern, the secondpattern, and the third pattern has a base angle and an aspect ratio, asshown in Table 1. Both base angles of each of the first pattern, thesecond pattern, and the third pattern are the same.

Examples 2 and 3

Polarizing plates were manufactured in the same manner as in Example 1except that the pattern group was composed of three patterns, that is, afirst pattern, a second pattern, and a third pattern sequentiallyarranged in the stated order without a flat section, and each of thefirst pattern, the second pattern, and the third pattern was an engravedtrapezoidal pattern and had a base angle and an aspect ratio, as shownin Table 1.

Example 4

A polarizing plate was manufactured in the same manner as in Example 1except that the pattern group was composed of two patterns, that is, afirst pattern and a second pattern, sequentially arranged in the statedorder without a flat section, and each of the first pattern and thesecond pattern was an engraved trapezoidal pattern and had a base angleand an aspect ratio, as shown in Table 1.

Example 5

A polarizing plate was manufactured in the same manner as in Example 1except that a flat section was formed between the engraved opticalpatterns in each pattern group. The flat section had a width of 5 μm.

Example 6

A polarizing plate was manufactured in the same manner as in Example 1except that a flat section was formed between the pattern groups. Theflat section had a width of 5 μm.

Example 7

A polarizing plate was manufactured in the same manner as in Example 1except that a flat section was formed between the engraved opticalpatterns in each pattern group (flat section having a width of 5 μm), aflat section was formed between the pattern groups (flat section havinga width of 5 μm), and the refractive indices of the first resin layerand the second resin layer were changed as listed in Table 1.

Example 8

A polarizing plate was manufactured in the same manner as in Example 1except that the refractive indices of the first resin layer and thesecond resin layer were changed as listed in Table 1.

Comparative Examples 1 and 2

Polarizing plates were manufactured in the same manner as in Example 1except that the pattern group was composed of three patterns, that is, afirst pattern, a second pattern, and a third pattern, sequentiallyarranged in the stated order without a flat section, and each of thefirst pattern, the second pattern, and the third pattern was an engravedtrapezoidal pattern and had a base angle and an aspect ratio, as shownin Table 1.

In Comparative Example 1, the first pattern, the second pattern, and thethird pattern had an aspect ratio of 1.0 and different base angles. InComparative Example 2, the first pattern, the second pattern, and thethird pattern had a base angle of 80° and different aspect ratios.

Comparative Example 3

A polarizing plate was manufactured in the same manner as in Example 1except that a trapezoidal pattern having an aspect ratio of 1.0 and abase angle of 85° was formed at an interface between the first resinlayer and the second resin layer without a flat section.

Comparative Example 4

A first resin layer (low-refractivity layer) was formed of a compositioncomprising a UV-curable resin (SHIN-A T&C Co., Ltd.) having a refractiveindex of 1.47. A second resin layer (high-refractivity layer) was formedof a composition comprising a UV-curable resin (SHIN-A T&C Co., Ltd.)having a refractive index of 1.62.

A polarizing plate was manufactured in the same manner as in Example 1except that trapezoidal patterns each having an aspect ratio of 1.0 anda base angle of 85° and flat sections were alternately formed at aninterface between the first resin layer and the second resin layer. Thetrapezoidal patterns had the same aspect ratio and the same base angle.FIG. 10 is a cross-sectional view of the polarizing plate of ComparativeExample 4. Referring to FIG. 10, the polarizing plate includes apolarizer 100; a pattern layer 400 including a first resin layer 420 anda second resin layer 410; and a protective film 300, which aresequentially stacked in the stated order, wherein trapezoidal patternsand flat sections are alternately formed at an interface between thefirst resin layer 420 and the second resin layer 410.

Models for measurement of viewing angle for the polarizing plates of theExamples and Comparative Examples were manufactured and viewing anglecharacteristics were measured at lateral angles shown in Table 1.

Light Source-Side Polarizing Plate

A polarizer was manufactured by stretching a polyvinyl alcohol film tothree times an initial length thereof at 60° C., followed by dyeing withiodine and stretching the dyed film to 2.5 times in a boric acidsolution at 40° C. Then, a polarizing plate was manufactured by bondingtriacetylcellulose films (thickness: 80 μm) to both surfaces of thepolarizer via a bonding agent for polarizing plates (Z-200, NipponGoshei Co., Ltd.). The manufactured polarizing plate was used as a lightsource-side polarizing plate.

Viewer-Side Polarizing Plate

As a viewer-side polarizing plate, each of the polarizing platesmanufactured in the Examples and Comparative Examples was used.

Module for Liquid Crystal Display

The light source-side polarizing plate was attached to a lower surfaceof a liquid crystal panel and the viewer-side polarizing plate wasattached to an upper surface thereof. Here, the viewer-side polarizingplate was disposed such that the protective film of the viewer-sidepolarizing plate was placed at the outermost periphery from the uppersurface of the liquid crystal panel. Then, a module for liquid crystaldisplays was manufactured by placing a light-collecting backlight unitincluding an inverse prism optical sheet at a lower side of the lightsource-side polarizing plate. In a white mode, a brightness profile asindicated by a dash-dotted line of FIG. 8 can be obtained by calculatingand graphing the ratio of brightness at a lateral side to brightness ata front side (0°) with respect to light emitted from thelight-collecting backlight unit. Referring to FIG. 8, the percentageratio (W_(30°)) of brightness (L_(30°)) at a lateral side (30°) tobrightness (L_(0°)) at a front side (0°) was 11% and the percentageratio (W_(60°)) of brightness (L_(60°)) at a lateral side (60°) tobrightness (L_(0°)) at a front side (0°) was 0%.

Brightness values from the front side (0°) to a right lateral side (90°)and a left lateral side (−90°) were measured in a white mode using anEZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Co., Ltd.).

The ratio of brightness at a lateral side to brightness in a front side(0°) in a white mode was calculated and results are shown in FIG. 11 toFIG. 22.

In a white mode, the percentage ratio of brightness at a lateral side(30°) to brightness at a front side (0°), the percentage ratio ofbrightness at a lateral side (45°) to brightness at a front side (0°),and the percentage ratio of brightness at a lateral side (60°) tobrightness at a front side (0°) were calculated and shown in Table 1.

TABLE 1 Example Comparative Example 1 2 3 4 5 6 7 8 1 2 3 4 First Base75 75 75 75 75 75 75 75 75 80 85 85 pattern angle Aspect 1.0 1.0 1.0 1.01.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 ratio Second Base 80 80 80 80 80 80 8080 80 80 — — pattern angle Aspect 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.01.5 — — ratio Third Base 85 85 85 — 85 85 85 85 85 80 — — pattern angleAspect 1.0 1.5 2.0 — 1.0 1.0 1.0 1.0 1.0 2.0 — — ratio Refractive Second1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.65 1.47 1.47 1.47 1.62 index resinlayer First 1.62 1.62 1.62 1.62 1.62 1.62 1.62 1.45 1.62 1.62 1.62 1.47resin layer Flat section in Absent Absent Absent Absent Present AbsentPresent Present Absent Absent Absent Present pattern group Flat sectionAbsent Absent Absent Absent Absent Present Present Present Absent AbsentAbsent Present between pattern group Viewing W30° 58 61 67 48 34 30 3240 22 73 26 23 angle W45° 44 46 48 41 43 41 29 44 26 70 9 6 W60° 31 3131 25 31 31 31 32 31 27 0 0 Result FIG. FIG. FIG. FIG. FIG. FIG. FIG.FIG. FIG. FIG. FIG. FIG. 11 12 13 14 15 16 17 18 19 20 21 22

*In Table 1, the base angle is represented in degrees (°) and theviewing angle is represented in percentage (%).

As shown in Table 1 and FIG. 11 to FIG. 18, the polarizing plateaccording to the present invention achieved improvement in viewing angleat all of lateral sides (30°, 45°, 60°), and had low deviation inviewing angle characteristics at the lateral sides (30°, 45°, 60°) inapplication to a liquid crystal display including a light-collectingbacklight unit.

By contrast, the polarizing plate of Comparative Example 1, in which atleast two patterns of the pattern group had different base angles andthe same aspect ratio, failed to improve viewing angle characteristicsat all of lateral sides (30°, 45°, 60°), as shown in Table 1 and FIG.19. In addition, the polarizing plate of Comparative Example 2, in whichat least two patterns of the pattern group had different aspect ratiosand the same base angle, failed to improve viewing angle characteristicsat a lateral side (60°) and exhibited larger deviation in viewing anglecharacteristics at a lateral side (60°) than at a lateral side (30°) andat a lateral side (45°), as shown in Table 1 and FIG. 20.

Further, the polarizing plate of Comparative Example 3, in which eachpattern of the pattern group had the same aspect ratio and the same baseangle, failed to improve viewing angle characteristics at all of lateralsides (30°, 45°, 60°) and exhibited no brightness, particularly at alateral side (60°), as shown in Table 1 and FIG. 21. Further, thepolarizing plate of Comparative Example 4, in which each pattern of thepattern group had the same aspect ratio and the same base angle and hada flat section therebetween, failed to improve viewing anglecharacteristics at all of the lateral sides (30°, 45°, 60°) andexhibited no brightness, particularly at a lateral side (60°), as shownin Table 1 and FIG. 22.

(1) A module for liquid crystal displays was manufactured using thepolarizing plate of Example 4 in the same manner as in measurement ofviewing angle in Table 1. Brightness at a front side (0°) of thespherical coordinate system was measured in a white mode and a blackmode using an EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Co., Ltd.). Aratio (A1) of brightness in the white mode to brightness in the blackmode was calculated.

With respect to a module for liquid crystal displays manufactured in thesame manner except that light source-side polarizing plates wereattached to both sides of a liquid crystal panel, a ratio (A2) ofbrightness in the white mode to brightness in the black mode wascalculated in the same manner.

The percentage ratio (contrast ratio) of A1 to A2 was calculated andshown in Table 2.

As obtained by measuring brightness values at a lateral side (30°) andat a lateral side (60°) instead of measuring brightness at a front side(0°), the percentage ratio (contrast ratio) of A1 to A2 was calculatedand shown in Table 2.

(2) A module for liquid crystal displays was manufactured using thepolarizing plate of Example 4 in the same manner as in Table 1 exceptthat a typical backlight unit including a normal prism optical sheet wasprovided to a lower side of the light source-side polarizing plate. In awhite mode, a brightness profile as indicated by a solid line of FIG. 8could be obtained by calculating and graphing the ratio of brightness ata lateral side to brightness at a front side (0°) with respect to lightemitted from the typical backlight unit. Referring to FIG. 8, thepercentage ratio (W_(30°)) of brightness at a lateral side (30°) tobrightness at a front side (0°) was about 52% and the percentage ratio(W_(60°)) of brightness at a lateral side (60°) to brightness at a frontside (0°) was about 13%.

W_(30°), W_(45°), and W_(60°) were calculated in the same manner andshown in the following Table 2 and FIG. 23.

The percentage ratios of A1 to A2 at a front side (0°), at a lateralside (30°), and at a lateral side (60°) were calculated in the samemanner as in (1) and are shown in the following Table 2.

Table 3 shows percentage values of W_(30°) and W_(60°) for alight-collecting backlight unit and a typical backlight unit.

TABLE 2 Viewing angle Contrast ratio (%) characteristics (%) FrontLateral Lateral W30° W45° W60° side (0°) side (30°) side (60°) Inapplication 48 41 25 98 120 450 to light - collecting backlight unit Inapplication 61 52 41 36 108 407 to typical backlight unit

TABLE 3 Brightness profile W30° W60° Light-collecting backlight 11 0unit Typical backlight unit 52 13

As shown in Table 3, it can be seen that the light-collecting backlightunit and the typical backlight unit exhibit completely differentbrightness profiles at a lateral side 30° and at a lateral side 60°.

As shown in Table 2, it could be seen that, in application of thepolarizing plate according to the present invention to a liquid crystaldisplay including a light-collecting backlight unit, the liquid crystaldisplay had improved viewing angle characteristics at all of lateralsides (30°, 45°, 60°) while improving front contrast and lateralcontrast.

By contrast, as shown in Table 2 and FIG. 23, in application of thepolarizing plate according to the present invention to a liquid crystaldisplay including a typical backlight unit, the liquid crystal displaysuffered from significant reduction in front contrast and exhibited lessimprovement in lateral contrast than the liquid crystal displayemploying the light-collecting backlight unit. This result shows thatthe polarizing plate according to the present invention effectivelyoperates in application to the liquid crystal display including thelight-collecting backlight unit.

Accordingly, embodiments of the present invention provide a polarizingplate capable of improving brightness, viewing angle, and contrast ratioat a front side and a lateral side in application to a liquid crystaldisplay including a light-collecting backlight unit.

Further, embodiments of the present invention provide a polarizing platecapable of improving front contrast ratio, lateral contrast ratio, andexternal appearance in application to a liquid crystal display includinga light-collecting backlight unit.

Further, embodiments of the present invention provide a polarizing platecapable of reducing deviation in a ratio of brightness at a lateral sideto brightness at a front side depending upon an angle of the lateralside in application to a liquid crystal display including alight-collecting backlight unit.

Further, embodiments of the present invention provide a liquid crystaldisplay that includes a light-collecting backlight unit, can improvebrightness, viewing angle and contrast ratio at a front side and alateral side, and can reduce deviation in ratio of brightness at alateral side to brightness at a front side depending upon an angle ofthe lateral side.

It is to be understood that, although some example embodiments have beendescribed herein, various modifications, changes, alterations, andequivalent embodiments can be made by those skilled in the art withoutdeparting from the spirit and scope of the present invention.

What is claimed is:
 1. A polarizing plate comprising: a polarizer; and apattern layer on a light exit surface of the polarizer, wherein thepattern layer comprises a first resin layer and a second resin layersequentially arranged on the polarizer, a pattern portion is located atan interface between the first resin layer and the second resin layerand is composed of at least two pattern groups repeatedly arrangedtherein, each of the pattern groups comprising at least two engravedoptical patterns, at least two adjacent pattern groups of the patterngroups having a same configuration, at least two of the engraved opticalpatterns in each of the pattern groups have different aspect ratios anddifferent base angles, and the engraved optical patterns in the patterngroups are consecutively arranged without a flat section therebetween.2. The polarizing plate according to claim 1, wherein the engravedoptical patterns have an aspect ratio of about 0.3 to about 3.0.
 3. Thepolarizing plate according to claim 1, wherein the engraved opticalpatterns in the pattern groups have a difference of about 0.5 or morebetween a maximum aspect ratio and a minimum aspect ratio.
 4. Thepolarizing plate according to claim 1, wherein the engraved opticalpatterns have a base angle of about 60° to about 90° .
 5. The polarizingplate according to claim 1, wherein the engraved optical patterns in thepattern groups have a difference of about 5° or more between a maximumbase angle and a minimum base angle.
 6. The polarizing plate accordingto claim 1, wherein the engraved optical patterns have a flat surface ata top portion thereof and an N-sided polygonal cross-sectional shape, Nbeing an integer from 4 to
 10. 7. The polarizing plate according toclaim 1, wherein a flat section is absent or further formed between twoimmediately adjacent pattern groups.
 8. The polarizing plate accordingto claim 1, wherein the engraved optical patterns extend in a stripeshape in a longitudinal direction thereof.
 9. The polarizing plateaccording to claim 1, wherein an angle defined between a longitudinaldirection of the engraved optical pattern and an absorption axis of thepolarizer is from about −20° to about 20° , from about 70° to about 110°, or from about −70° to about −110° , where the absorption axis of thepolarizer is defined as 0° .
 10. The polarizing plate according to claim1, wherein an absolute value of a difference in refractive index betweenthe first resin layer and the second resin layer is about 0.05 or more.11. The polarizing plate according to claim 1, wherein a number of theengraved optical patterns in each of the pattern groups is from 2 to 10.12. The polarizing plate according to claim 1, wherein each of thepattern groups is composed of a total of two optical patterns comprisinga first pattern and a second pattern as the engraved optical patterns,and the first pattern and the second pattern have different base anglesand different aspect ratios.
 13. The polarizing plate according to claim1, wherein each of the pattern groups is composed of a total of threeoptical patterns comprising a first pattern, a second pattern, and athird pattern, as the engraved optical patterns, and at least two of thefirst pattern, the second pattern, and the third pattern have differentbase angles and different aspect ratios.
 14. The polarizing plateaccording to claim 1, wherein the first resin layer is a filling portionfilling at least part of the engraved optical patterns or a layercomprising the filling portion.
 15. The polarizing plate according toclaim 1, further comprising a protective film stacked on at least one ofa light exit surface and a light incident surface of the pattern layer.16. The polarizing plate according to claim 15, further comprising atleast one surface treatment layer selected from among a hard coatinglayer, a scattering layer, a low reflectivity layer, an ultra-lowreflectivity layer, a primer layer, an anti-fingerprint layer, anantireflection layer, and an antiglare layer on at least one surface ofthe protective film.
 17. A liquid crystal display comprising thepolarizing plate according to claim
 1. 18. The liquid crystal displayaccording to claim 17, comprising a backlight unit, a light source-sidepolarizing plate, a liquid crystal panel, and the polarizing platesequentially stacked in the stated order, the backlight unit comprisinga light-collecting backlight unit comprising an inverted prism sheet.19. A polarizing plate comprising: a polarizer; and a pattern layer on alight exit surface of the polarizer, wherein the pattern layer comprisesa first resin layer and a second resin layer sequentially arranged onthe polarizer, a pattern portion is located at an interface between thefirst resin layer and the second resin layer and is composed of at leasttwo pattern groups repeatedly arranged therein, each of the patterngroups comprising at least two engraved optical patterns, at least twoadjacent pattern groups of the pattern groups having a sameconfiguration, at least two of the engraved optical patterns in each ofthe pattern groups have different aspect ratios and different baseangles, and the at least two adjacent pattern groups are consecutivelyarranged without a flat section therebetween.